Electronic computing devices have become increasingly important to data computation, analysis and storage in our modern society. Modem direct access storage devices (DASDs), such as hard disk drives (HDDs), are heavily relied on to store mass quantities of data for purposes of future retrieval. As such long term data storage has become increasingly popular, and as the speed of microprocessors has steadily increased over time, the need for HDDs with greater storage capacity to store the increased amount of data has also steadily increased.
Consequently, there are seemingly constant development efforts to improve the areal density of the media implemented in hard disk drives, where the areal density is typically measured as the product of bits per inch (“BPI”) and tracks per inch (“TPI”). BPI refers to the number of bits that can be written and later reread per linear inch along a track, whereas TPI refers to the number of individual tracks per radial inch. Improvements in areal density in turn lead to higher demands and stricter requirements put on the corresponding magnetic read/write heads. Furthermore, additional and significant improvements are taking place which fundamentally change how HDDs record data onto the media, such as with perpendicular magnetic recording (PMR) and thermally assisted recording (TAR).
Such advancements in areal density result in much tighter tolerances regarding read/write head performance. That is, the precision with which the head and associated actuation system operate need to improve as areal densities increase. Consequently, more exhaustive and efficient head acceptance testing would be beneficial.
It is common for an HDD developer or manufacturer to perform oscillation testing during HDD production, to detect any seek problems associated with the magnetic read/write heads produced. Such oscillation testing procedures move the head being tested across a recording media, consecutively between one side of the media to the other side of the media and progressively from outer data blocks to inner data blocks, while writing and reading data blocks at the target locations on the disk, all the while converging toward the middle of the writeable media. The target locations with such a procedure are logical block addresses (“LBA”s). However, such oscillation tests only detect the mechanics of seek read/write problems, rather than detecting off track write problems, and with a test time on the order of 0.33 hours/head.